SAS said negotiations with union representatives over working conditions had been "unsuccessful," according to the statement.

Some 800 crew members walked off the job at 0300 GMT Friday after negotiators failed to reach an agreement over terms and conditions linked to SAS' offer of a 10.2 percent pay rise over three years.

The cabin crew union, which belongs to the Swedish Salaried Employees' Union (HTF), is calling for improvements in working conditions including changes in staff meal times.

"The future of SAS Sweden and the SAS group is at risk, and consequently the future of maybe 3,000 HTF (union) members," Anders Ehrling, SAS Sweden's chief executive said.

SAS reported a loss in the first quarter of the year.

It came close to bankruptcy several years ago amid a global crisis in the airline sector following the September 11, 2001 attacks in the United States and the advance of low-cost carriers, but managed to return to profit last year thanks to several drastic savings measures.

The carrier on Thursday cancelled 250-300 domestic and European flights for Friday because of the strike.

In the event that the dispute continues, HTF has agreed not to strike during the peak holiday period from June 11 to August 12, and to exempt SAS charter traffic.

Some 20,000 passengers were estimated to be hit by the strike on Friday and almost 10,000 on Saturday. Each day of strike action is estimated to cost SAS over 20 million kronor ($2.92 million) not including possible passenger compensation.